Magnetic field strength detectors have been used in various industries to detect the presence of spurious, unwanted and even sometimes dangerous levels of magnetic fields. In many instances the magnetic field strength detector provided information or warning to protect against excessive exposure of films, tapes, magnetic disks to magnetic fields.
U.S. Pat. No. 3,604,373 describes a storage cabinet system in which magnetic field strength detectors were placed within the cabinet to signal an excessive level of magnetism by audio and visual alarms.
U.S. Pat. No. 7,068,030 describes a magnetic field strength detector that may be used to measure the strength of a magnetic field generated by a degaussing device, or to confirm that a particular medium was exposed to a magnetic field with strength adequate to degauss the medium.
Magnetic field strength detectors have been used to detect excessive magnetic fields that could damage sensitive medical equipment. U.S. Pat. No. 4,954,812 describes a stand-alone device for use in preventing accidental exposure of magnetically sensitive equipment to large magnetic fields produced by Magnetic Resonance Imagining devices. This patent describes a device designed to be externally mounted onto a vertical stand, using a vise grip arrangement, which supports magnetically sensitive equipment. Three Hall sensors are arranged in a horizontal plane with an angle of 120 degrees between each sensor. Mechanical potentiometers are used for calibration at the site of the end-user. U.S. Pat. No. 4,95,4812 describes the use of absolute value circuitry in the signal paths of the Hall sensors. The devices described in the patent have audible alarms as well as light emitting diode (LED) bar graph displays for a dynamic visual indication of the magnitude of the magnetic field being detected. The devices are powered by two 9V batteries connected in series to develop a bipolar supply of ±9V.
Therefore, there is a need in the industry for a device to assist manufacturers of instruments that are sensitive to magnetic fields, especially OEM medical equipment manufacturers, to identify and troubleshoot equipment anomalies by recording the magnetic field to which a particular instrument or medical equipment was exposed where the detection device is integral to the sensitive instrument.